Introduction
A green roof is a roof that is partially or wholly covered with a growing medium to absorb rainwater, creating a natural habitat for organisms, and creating an aesthetic appeal (Cantor 16). Examples of vegetation used in green roofs include shrubs, trees, flowers, succulent plants, and grass. Designers used waterproof membranes to protect buildings from the devastating effects of water that infiltrates the surfaces during rainy periods. Environmentalists and proponents of green roofs argue that they improve air quality and reduce the heat absorbed and retained by urban environments (Hopkins and Goodwin 53). These types of roofs have several advantages compared to conventional roofs. In addition, they play a significant role in environmental conservation. Green roofs supplement traditional vegetation, improve environmental aesthetics, promote cooling through evapotranspiration, and utilize neglected spaces. The creation of green roofs is a phenomenon that is common in many countries including the United States, Canada, France, the United Kingdom, Sweden, Germany, Israel, Switzerland, and Egypt among others.
Types of green roofs
Two main types of green roofs are widely created in buildings. They include intensive and extensive green roofs and are distinguished by their profiles, designs, and intended purposes (Cantor 18). The two types are different in various ways. Extensive green roofs are characterized by thin layers of soil, small plant types, low costs of maintenance and creation, and predominantly inorganic soil (Hopkins and Goodwin 37). On the other hand, intensive green roofs are characterized by thick soil layers, a wide variety of plants, high maintenance and creation costs, and an equal composition of organic and inorganic soil. A semi-intensive green roof is an intermediate between the two types that has greater diversity than that of the extensive roof and is lesser than that of the intensive green roof. They are created by combining aspects of both extensive and intensive roofs and are usually established in order to enjoy the environmental benefits that they provide as well as the diversity of vegetation they offer without inflated costs (Hopkins and Goodwin 38). Green roofs are either flat or sloping depending on the structure of the building. Sloping gardens improve water drainage and reduce water infiltration. On the other hand, flat roofs improve water retention and as such eliminate the need for an irrigation system.
Components of a green roof
A green roof contains several components that conventional roofs lack. These include structural support, a waterproofing membrane to protect the building, a drainage layer, a layer to protect the vegetation’s roots, a vapor control system, and an artificial planting media (Snodgrass and McIntyre 35). A thermal insulation system is also an important component. Drought-resistant plants distinguish green roofs from conventional roofs. Therefore, they are the most important component. A waterproofing membrane ensures that the surface of the building is dry at all times in order to prevent water from infiltrating the building (Snodgrass and McIntyre 35). The membrane should possess qualities that prevent air and root penetration. The thermoplastic PVC membrane is the most commonly used type of waterproofing membrane in the creation of garden roofs because of its durability and hardness (Hopkins and Goodwin 40). In addition to the membrane, a root barrier can be added to prevent roots from penetrating.
Advantages of extensive and intensive green roofs
Each of the aforementioned green roofs is preferred for certain reasons depending on the tastes of developers and the intended purpose. Extensive green roofs are preferred by many people because they are light in weight, can be replaced easily, costs little money to create and maintain, and usually do not require the inclusion of an irrigation system (Cantor 21). They are usually created on flat surfaces. Therefore, they increase water retention because little of it flows through the drainage system. In addition, they are appropriate for large spaces. On the other hand, intensive green roofs are liked for their great plat diversity, exceptional insulation systems, rainwater management, and application of various types of designs (Snodgrass and McIntyre 29). In addition, they allow biodiversity because they contain a variety of plant and animal species in a single habitat.
Disadvantages
Green roofs have several advantages. However, they have disadvantages too. The cost of constructing a green roof is higher than that of constructing a conventional roof because of the costs of materials (Hopkins and Goodwin 44). Soil and the water that is retained during rainy periods increase the stress exerted on the building’s stricture. This lowers the suitability of establishing intensive green roofs on many buildings because they cannot support their weight. Green roofs cause structural damages that can be difficult to identify and repair (Snodgrass and McIntyre 42). Despite the use of a membrane to prevent root penetration, some roots bypass the membrane and cause roof leaks that are difficult to repair (Cantor 27). Green roofs are very complicated and therefore identifying damages is tough. Some plants have weak root systems and therefore fail to survive the strong weeds that are common on rooftops.
Benefits
Green roofs serve various purposes that account for their widespread creation in many buildings. They provide shade, improve aesthetics, and cool the air (Hopkins and Goodwin 57). This role is accomplished through the process of evapotranspiration that lowers the temperatures of roof surfaces and air. Urbanization has resulted in a trend that involves clearing vegetation in order to create space for building infrastructure. This leaves the soil bare and increases tea ret of evaporation that contributes to the high temperatures experienced in urban areas. One of the reasons for the installation of green roofs in private residences is their ability to absorb heat from surfaces and thus act as insulators (Cantor 32). This insulation helps to enhance cooling. On the other hand, the cooling effect results in the use of high amounts of energy for warming houses especially in cold weather (Hopkins and Goodwin 57). The roofs are particularly beneficial during hot weather because they absorb heat and thus improve indoor comfort. Green roofs have positive environmental outcomes because they reduce air pollution by lowering greenhouse gas emissions (Cantor 33). This is achieved by lowering the need for indoor air conditioning. Moreover, processes such as photosynthesis consume carbon dioxide and other gases that constitute greenhouse emissions (Hopkins and Goodwin 58). Another benefit of these roofs is that they improve the durability of roofs by lowering their exposure to direct sunlight and reducing the effects of rainwater. Green roofs control runoffs and filter pollutants from rainfall thus improving the quality of water that is harvested for storage. This leads to better public health outcomes because apart from filtering pollutants, they also lower pollution. They also promote health by protecting people from exposure to direct sunlight, too much heat, and improving indoor comfort. Finally, they improve environmental aesthetics and create habitats for many organisms such as birds and insects (Cantor 35). Other benefits include improvement of energy efficiency, higher durability f roofing membrane, fire retardation, reduction of electromagnetic radiation, and noise reduction. The aesthetics provide by green roofs improve the marketability of buildings especially those constructed to serve as private residences. In addition, reinforcing buildings so that they can support intensive gardens is costly and time-consuming. Green roofs have high maintenance costs depending on the type (Hopkins and Goodwin 59). For instance, vegetation might penetrate waterproof membranes and necessitate replacement that increases costs of maintenance. Finally, green roofs create new habitats for organisms. Pests could inhabit the roof and infiltrate the buildings and cause massive destruction to clothes and food.
Conclusion
The establishment of green roofs is a phenomenon that is common in many developed countries. They comprise growing mediums such as grass and plants that serve various purposes. Green roofs have several benefits that make them more common than conventional roofs in certain areas. They provide shade, improve aesthetics, cool the air, reduce air pollution, increase the durability of roofs, and act as insulators. They also improve public health by increasing comfort, protecting people from exposure to direct sunlight and high temperatures, and filtering pollutants from rainfall thus providing clean drinking water. There are two main types of green roofs namely extensive and intensive. They are grouped based on their profile and the type of vegetation used. Extensive roofs have thick soil layers and diverse plants while intensive roofs have thin soil layers and limited plant diversity. Despite the aforementioned advantages, green roofs have disadvantages too. They are costly to establish and maintain and can cause structural damages that are not easily detected. Green roofs have more advantages and disadvantages. Therefore, they are a good alternative to traditional roofs.
Works Cited
Cantor, Steven. Green Roofs in Sustainable Landscape Design. New York: W.W. Norton & Company, 2008. Print.
Hopkins, Graeme, and Goodwin Christine. Living Architecture: Green Roofs and Walls. New York: Csiro Publishing, 2011. Print.
Snodgrass, Edmund, and McIntyre Linda. The Green Roof manual: A Professional Guide to Design, Installation, and Maintenance. New York: Timber Press, 2010. Print.